As people have become more accustomed to electronic methods of communication, data manipulation and information processing in their jobs and in their personal lives, the need for portability of the electronic devices which perform these tasks has increased. One goal, for example, has been to produce quite compact devices which have the combined capabilities of a desktop or laptop computer, a cellular telephone, a fax machine, and more. Such devices are commonly referred to as personal communicators.
The technological limits of portability have often been dominated by the limitations of power supply technology--that is, by the weight and size limitations of current battery technology. However, an area that has been given less attention is the input keyboard usually associated with these devices. Most designs of portable computing devices have retained the use of the conventional "QWERTY" keyboard because of its familiarity. However, to include the QWERTY keyboard in a portable computing device limits the designer's ability to reduce the size of such a device, since sufficient width is required to accommodate two hands side by side. QWERTY keyboards which are smaller than 8 inches across tend to be very difficult to use in a touch-typing mode quickly. Thus, a one-finger "hunt and peck" action may be required. Moreover, it is necessary to take care with such small keyboards to avoid fingers touching more than one key at a time.
One approach that is presently being pursued is to eliminate the need for a keyboard altogether. In particular, portable computing devices are now available which accept handwritten input, provided with use of a stylus or similar pen-like tool. These devices make use of handwriting recognition software to interpret the user's handwritten input and to convert it to an equivalent internal representation (e.g., in ascii text form).
At least two problems result from this approach. First, the algorithmic complexity required for reasonably accurate handwriting recognition currently requires substantially more processing power than do many of the applications otherwise provided on such portable computing devices. Therefore, these devices may need to be far more costly with the use of conventional handwritten input techniques than with keyboard-based input techniques. Moreover, the power requirements for a processor capable of performing reasonably accurate handwriting recognition can be substantial.
Second, most handwriting recognition software available today has an input error rate significantly higher than that typically achievable with the use of keyboard input. Although sophisticated handwriting recognition techniques often include error correction capability, the complexity and variability of handwritten input often results in less accurate input text than does text typed in through a keyboard.
One alternative approach which has been suggested is a stylus-based keyboard design in which text is entered by touching (or otherwise coupling) a stylus to successive keys on a keyboard. A device containing such a stylus-based keyboard can be designed to be comparable in size to a device based on handwriting recognition. Moreover, it can have a much lower error rate with significantly less processing power requirements. Thus, stylus-based keyboards can allow for the construction of low-end (i.e., low cost) portable computing devices.